The behaviour of reinforced concrete frames with masonry wall infills is influenced a lot by the stiffness and strength difference between the frame and the infill, causing early detrimental damage ...to the infill or to the critical concrete columns. The paper reports the results from shake table seismic tests on a full-scale reinforced concrete (RC) frame building with modified hollow clay block (orthoblock brick) infill walls, within INMASPOL SERA Horizon 2020 project. The building received innovative resilient protection using Polyurethane Flexible Joints (PUFJs) made of polyurethane resin (PU), applied at the frame-infill interface in different schemes. Further, PUs were used for bonding of glass fibre grids to the weak masonry substrate to form Fibre Reinforced Polyurethanes (FRPUs) as an emergency repair intervention. The test results showed enhancement in the in-plane and out-of-plane infill performance under seismic excitations. The results confirmed remarkable delay of significant infill damages at very high RC frame inter-story drifts as a consequence of the use of PUFJs. Further, the PUFJ protection enabled the resilient repair of the infill even after very high inter-story drift of the structure up to 3.7%. The applied glass FRPU system efficiently protected the damaged infills against collapse under out-of-plane excitation while they restored large part of their in-plane stiffness.
It has been recognized that the shear capacity of old bridges can play a crucial/key role in evaluating their structural safety. Determination of the shear capacity of critical cross‐sections ...presents a much greater challenge than the assessment of their bending capacity.
Due to abovementioned problems, the shear capacity of shorter reinforced concrete bridges with T‐beams has been evaluated with various models. Four different models were examined, the currently valid Eurocode 2, draft of the new version of Eurocode 2, the currently valid Eurocode 8‐3 and the model corresponding to modified compression field theory (MCFT). According to all the models, the capacity of deck of existing reinforced concrete bridge was calculated. This bridge was previously inspected and the actual amount and shape of the shear and bending reinforcement was determined.
The results obtained with different models were compared and the typical parameters which influence the shear capacity were analyzed. The results in terms of shear capacity show that different models can give quite different results for the same bridge.
The efficiency of strengthening of unreinforced hollow clay block masonry buildings with fibre reinforced mortar coatings has been investigated. A full scale three-storey building model and a series ...of accompanying walls have been built and tested. Reference unstrengthened, and strengthened specimens of each type have been tested by subjecting them to cyclic shear at constant compressive load. First, the three-storey model was tested in its original state until the maximum resistance was attained and major, but still repairable damage, developed in the walls. Then, the damaged model was strengthened with fabric reinforced cementitious mortar coating and re-tested up to near collapse limit state. Typical storey mechanism was observed in original and strengthened state, with the majority of damage concentrated in the walls of the bottom storey. Diagonally oriented shear cracks prevailed in the elements in the direction of loading. The behaviour of single walls in cyclic shear tests was similar to that observed in the piers of the building models. The analysis of test results indicated that the resistance and displacement capacity of unreinforced masonry structures of the particular type tested can be significantly improved if delamination and separation of coating is prevented. Finally, a calculation model for the assessment of seismic resistance of reference and strengthened building model is presented and the comparison between calculated and experimental results discussed.
This paper presents results of in-plane shear tests carried out at the ZAG laboratory in Ljubljana (Slovenia) on a RC frame with masonry infill made of clay blocks (KEBE OrthoBlock). The frame was ...loaded with constant vertical loads at the top of the columns and then by gradually increasing horizontal cyclic loads at the top beam level. Acquired forces and measured displacements allowed capturing hysteretic behavior for determination of dissipation energy. In addition, two Digital Image Correlation (DIC) systems, Aramis and the CivEng Vision, were used to visualize the behavior of the tested specimens, with an emphasis on computing locally required information about the behavior of highly deformable interfaces. Three types of specimens were tested in-plane: the reference specimen in form of plain RC frame, the reference specimen with constructed masonry infill without any strengthening and the specimen, previously damaged and then strengthened on both sides using glass mesh bonded to the infill and the RC frame using flexible adhesive made of polyurethane matrix (Glass Fiber Reinforced PolyUrethane - GFRPU system). The strengthening process, allowed the specimen to withstand additional cyclic loads, reaching a maximum drift of 3.6 % without serious damage disqualifying the structure from further exploitation. The GFRPU strengthening system was found to be highly effective in preventing infill collapse of damaged masonry infill wall during in-plane loading. Additionally, the results of extended thermal analysis of PU are presented as polymers are, in general, a material, poorly resistant to heat. However, the analyzed PU manifested stable properties up to 200 degrees Celsius, which makes this material promising in civil engineering applications at elevated temperatures.
•In-plane push-over cyclic tests of RC frame strengthened by flexible GFRPU system.•Maximum frame drift of the value 3.6 %, without serious damage.•GFRPU strengthening system was very effective and resistant to out-of-plane forces.•FRPU matrices made of PU are resistant to elevated temperatures.•Local large deformations of GFRPU system identified by DIC measurements.
The paper presents an experimental test of a nearly full-scale three-storey model of a confined masonry structure. The walls were constructed using newly developed clay masonry blocks, with large ...holes filled with thermal insulation and polyurethane glue instead of mortar. In the construction,relatively thick 38 cm walls and large tie-columns with 25 cm × 25 cm plan dimensions. The test model was built as confined masonry according to Eurocode 8. The innovative materials and construction were developed for thermal efficiency and the test was intended to verify the structural response. The model, test setup, and test procedures are described, and the results of the tests are analysed. The building responded primarily in shear, and ultimately failed in the ground floor in a storey mechanism, but there was also substantial damage on the floor above. Due to the non-standard dimensions of the tie-columns and because masonry was thicker than the tie-columns, the in-plane loaded walls developed an interesting response mechanism in which protruding masonry sheared off. Although this did not significantly impact the overall response, it led to the earlier onset of the significant damage limit state of the structure. The model responded well with wide hysteretic loops and distributed damage, which indicated large energy dissipation capacity, and the response envelopes showed gradual strength deterioration after peak load. The response of the model was quantitatively estimated using the N2 method. Calculations showed that the tested model could withstand a design seismic load corresponding to a 0.21 g peak ground acceleration with significant damage and almost 0.52 g before collapsing. The overstrength was estimated at 1.71.
•Laboratory test of a nearly full-scale three storey confined masonry building model.•Innovative new masonry construction from vertically perforated blocks and polyurethane glue.•Response was mainly by shear, but with significant energy dissipation and slow post peak strength degradation.•Significant damage occurs at 0.21 g, near collapse at 0.52 g, and the overstrength was about 1.71.•The seismic response of the system was good, but could be improved by improving the interaction with the tie-columns.
Seismic behaviour of masonry buildings, built of low compressive strength units, is discussed. Although such materials have already been tested and approved for use from mechanical and thermal ...insulation point of view, the knowledge regarding their structural behaviour is still lacking. In order to investigate the resistance and deformation capacity of this particular type of masonry construction in seismic conditions, a series of eight walls and model of a two-storey full scale confined masonry building have been tested by subjecting the specimens to cyclic shear loads. All tests were conducted under a combination of constant vertical load and quasi static, cyclically imposed horizontal load. The behaviour of tested specimens was of typical shear type. Compared with the behaviour of plain masonry walls, the presence of tie-columns resulted into higher resistance and displacement capacity, as well as smaller lateral resistance degradation. The response of the model was determined by storey mechanism with predominant shear behaviour of the walls and failure mechanism of the same type as in the case of individual confined masonry walls. Adequate seismic behaviour of this particular masonry structural type can be expected under the condition that the buildings are built as confined masonry system with limited number of stories.
The paper presents the main results of the development project “Digitalization of monitoring the condition of bridge structures on highways and expressways in the Republic of Slovenia”. Within the ...project, test cases of the digitalized inspection method were carried out on three different concrete bridges. To enable validation of digitalization, a traditional and digital inspections for all three bridges have been conducted, focusing on the three important types of reinforced concrete bridges damages: delamination, cracks and reinforcement corrosion. The comparison of the results has shown that digital inspection can already strongly support bridge inspections, especially during detailed inspections, as it can, to some extent, completely replace the time‐consuming damage mapping. In addition, the analyses show that, already today, digital inspection is often economically justifiable.
Four experimental campaigns performed at ZAG over almost a decade and dealing with strengthening of masonry using FRPs are briefly presented. The campaigns show in-situ tests on strengthened walls in ...an actual building, the cyclic shear laboratory tests where different materials and FRP layouts were explored, use of innovative flexible materials instead of mortar or epoxy, and finally the test of a full scale building model where all aspects of strengthening a building using FRPs are investigated.
Abstract
Um das Schubtragverhalten von Mauerwerkswänden in Versuchen realistisch abzubilden, sollten die Versuchsrandbedingungen möglichst den Verhältnissen in Gebäuden entsprechen. Andernfalls ...würden in den Versuchen ein unrealistisches Verhalten und möglicherweise unzutreffende Bruchmechanismen erzielt. Zur Untersuchung des Einflusses unterschiedlicher Versuchsrandbedingungen wurden am ZAG Ljubljana acht Wände aus Ziegelmauerwerk mit Normalmauermörtel unter vier unterschiedlichen Randbedingungen auf Scheibenschub geprüft. Die Versuchsergebnisse zeigen den deutlichen Einfluss der Versuchsrandbedingungen auf die Tragfähigkeit und Verformungsfähigkeit der Wände.
Abstract
Experimental testing of seismic response of brick masonry walls under different boundary conditions
In order to reproduce the seismic response of masonry piers in laboratory cyclic shear tests, the boundary conditions need to be similar to those in actual buildings. If the similarity is not adequate, tests may predict unrealistic behaviour, and in the worst case, even unrealistic failure mechanisms. To study the effect of different boundary conditions, eight walls built with hollow clay units and general purpose mortar were tested under four different boundary conditions. The results show that different boundary conditions have a strong influence on force and displacement capacity of the walls.
Um das Schubtragverhalten von Mauerwerkswänden in Versuchen realistisch abzubilden, sollten die Versuchsrandbedingungen möglichst den Verhältnissen in Gebäuden entsprechen. Andernfalls würden in den ...Versuchen ein unrealistisches Verhalten und möglicherweise unzutreffende Bruchmechanismen erzielt. Zur Untersuchung des Einflusses unterschiedlicher Versuchsrandbedingungen wurden am ZAG Ljubljana acht Wände aus Ziegelmauerwerk mit Normalmauermörtel unter vier unterschiedlichen Randbedingungen auf Scheibenschub geprüft. Die Versuchsergebnisse zeigen den deutlichen Einfluss der Versuchsrandbedingungen auf die Tragfähigkeit und Verformungsfähigkeit der Wände.
Experimental testing of seismic response of brick masonry walls under different boundary conditions
In order to reproduce the seismic response of masonry piers in laboratory cyclic shear tests, the boundary conditions need to be similar to those in actual buildings. If the similarity is not adequate, tests may predict unrealistic behaviour, and in the worst case, even unrealistic failure mechanisms. To study the effect of different boundary conditions, eight walls built with hollow clay units and general purpose mortar were tested under four different boundary conditions. The results show that different boundary conditions have a strong influence on force and displacement capacity of the walls.
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